Method of and apparatus for testing properties of materials



E. M. IRWIN July 21, 1942.

METHOD OF AND APPARATUS FOR TESTING PROPERTIES OF MATERIALS 5Sheets-Sheet l Filed Aug. l2, 1940 July 21, 12942 E. M. IRWIN I2,290,330

METHOD OF AND `APPARATUS FOR TESTING PROPERTIES 0F MATERIALS v FiledAug. l2, 1940 3 She-ets-Sheet 2 July 21, 1942- E. M. IRWIN 2,290,330v

METHOD 0E AND APPARATUS EOE TESTING PRoPERTTEsIoE MATERIALS Filed Aug.12, 1940 5 sheets-sheet 3 BY I n Patented July 2l, 1942 PROPERTIES OFMATERIAL Emmett -M. Irwin, Lo

25 Claims.

My invention relates to a method and apparatus for testing theyproperties of materials.

It has been proposed, heretofore, to test the properties of materials,suchas magnetic mate-l rials for example, by utilizing the material tobe tested to aifect a circuit excited by an alternating current, andobserving the effect of the material upon the electrical characteristicsof the alternating current circuit or electrically related circuit, todetermine the presence of defects or the physical properties oi thematerial. In this manner materials have been tested to determine defectsin the material such as cracks, surface irregularities, internal flaws,blowholes, pipesresulting from inclusions of slag in rolling down thematerial from an ingot, and also to determine the effector heattreatment, hardness, chemical composition, and magnetic properties.'I'hese tests generally have been made by referring the observedmagnitudes to a known standard'by comparing the effect on thealternating current circuit of astandard specimen of -known propertieswith the eiect of a specimen of unknown properties to be tested, or bysimultaneous effects of the standard and the specimen to be tested onrelated alternating current circuits.

Unless the phase relation of the voltage and ng Beach, Calif., assignorto Malnetest Corporation, Long Beach, Calif., a corporation ofCalifornia Application August 12, 1940, serial No. 352,280

(c1. 17a-iss) late the measurements of phase angle and amplitude, whichresults in erroneous observations. Furthermore this procedure is almostimpossible to carry out effectively if the material being tested isbeing moved with respect to the alter- -nating current circuit, as isrequired in testing rods, pipes, or other long pieces of material,Abecause the changes in phase ordinarily would occur too rapidly topermit such observations. The failure to observe these rapid phasechanges has lead to erroneous results. i

An object of my invention is to provide an improved and more reliablemethod and apparatus for testing materials in which the material aiiectsan electrical characteristic of an altemating current circuit. Iaccomplish this by indicating a magnitude functionally related to thephase angle between an alternating currentand an alternating voltage ina circuit alTected by the material, and indicating a magnitudevfunctionally related to an alternating electrral characthe current inthe alternating current circuitaffected by the material is determined,the results observed inthese tests may be very misleading. A smallmagnitude of voltage or current may be indicated, when in fact themagnitude is large, because the measurement of the magnitude may be madein such phase relation as to give only a small magnitude, which ismerely a component 'part of the true larger magnitude. Furthermore,there is a relationship between the phase angle of the voltage and thecurrent in the alternating current circuit and the properties of thematerial being tested, so that one may measure the magnitude of anelectrical characteristic of the alternating current circuit with theimpression that the magnitude represents a condition or property of thematerial, whereas in fact if the phase relation were known it wouldindicate that the magnitude represented a different property than theone under consideration.

In some tests of this kind determinations have been made of the phaserelation between the voltage and the current in an alternating currentcircuit affected by the material tested. However,

the determinations have been made by constructing the phase relationfrom observed data. By this procedure it is difiicult to accuratelyreteristic of the circuit in timed relation to or simultaneously withand independently of indicating the magnitude related to the phaseangle.

,In this manner all indications are related to the phase relations inthealternating current circuit,A

which provides for greatly increased accuracy of results and facilitatesmore rapid testing of the material.

Another object of my invention is to provide in a testing system inwhich a material to be tested is moved with respect to an alternatingcurrent circuit, an improved method minimize the occurrence of erroneousobservations.

tested with recircuit, and covoltage or other and' apparatus to Iaccomplish this by providing a circuity excited by an alternatingcurrent source of supput from the amplifier in terms of phase angle.

Further objects and advantages of my invention will become apparent asthe following description proceeds, and the features of novelty whichcharacterize my invention will be pointed out with particularity. in theclaims annexed' to and forming a part of this specification.

In the drawings, Fig. l is a schematic diagram of an apparatus embodyingthe constructional portion of a record sheet or chart obtainedin theoperation of the recorder shown in Fig. 4; Fig. 6 is a sectional view onthe line of 46--6of Fig. 4; Fig. '7 is a diagrammatic view of theconstruction shown in Fig. 6 illustrating how one of the.

styluses is moved out of recording position with respect to the recordsheet when the' other stylus is moved into recording position withrespect thereto; Fig. 8 is a detail view of the `ioint between the endsof the steel ribbon which I prefif desired. may be a current amplifier,so long as the output therefrom through conductors 22 to a stationarysolenoid 23 of a recorder 24 is a function of an electricalcharacteristic of the secondary circuit associated with the secondarycoil I6.

The construction of the recorder 24 is clearly shown in Figs. l, 4. 6.'7, 8, 9, and 1I). In order -to record an amplitude functionally relatedto an electrical characteristic of the secondary circuit associated withthe secondary coil I6, the

. recorder 24 is provided with a stylus or pen 26 mounted on the lowerend of arm 26,V which is pivotally supported on the body of the recorderat 21. The horizontal arm 23 is rigidlyl attached to the vertical arm 26of the '.recorden,

and the outer end of the arm 26 is pivotally connected at 29 to a softiron armature 30 susof the arm 26.

erably employ as the endless band of the rey corder on which thestyluses are mounted; Fig. 9 is an enlarged cross sectional view of oneof the styluses or pens employed on the band of the phase recorder; andFig. l0 is an enlarged sectionalview on the line III-III of Fig. 6,showing the manner of mounting the rollers for supporting the band.

Referring to the drawings, in Fig. l I have shown schematically anentire system embodying the novel constructional features of myinvention, and also a system adaptable to carrying out my improvedmethod. A specimen I0 of magnetizable material, such as a sucker rodfrom an oil well, a drill pipe used in drilling oil wells, or othersuitable bar, is supported on rollers II and I2, so as to be movablelongitudinally. In order to move the specimen I0 as desired, it may bemoved on the rollers by hand, or by a driving motor I3, which keeps thespecimen I0 within the desired range of speed of movement. The specimenID is moved coaxially through primary windings I4 and I5 arranged onopposite sides of a secondary Winding I6. The windings I4 and I5 areWound in the same direction, so as to give an additive effect to theirampere turns. The windings I4, I5, and I6 are supported in coaxialrelation with the specimen I0 in any suitable manner, and provide forfree movement of the specimen through the coils. The windings I4 and I5are connected in series at I1 and across an alternating current sourceof supply I8. I have found it to be satisfactory to utilize thealternating current source of supply I8 at iifty cycle frequency, and acurrent voltage amplifier 2I. The voltage amplifier 2I,

pended within the stationary solenoid 23. The arms 26 and 26 arebalanced by a spring 23a, and a stop 23a limits the range of movement Arecord of the magnitude to be indicated by the stylus 25 on the recordmember or chart 3| is obtained by maintaining the Arecord sheet in'astretched condition in cooperative relation with the stylus 26 and closeto the opening 32 in the front of the recorder. I provide an upperroller 33 upon which the record sheet is wound, and a lower roller 34jfrom which the record sheet is wound, the rollers 33 and 34 beingsupported in suitable bearings. The edges of the record sheet preferablyare perforated at 3Ia along the edges to prevent slipping by engagementwith suitable teeth associated with the rollers 33 and 34. The rollers33 and 34 are geared together by an arrangement including a slip clutchor belt, so that upon driving the rollers 33 and 34 to move the recordsheet as indicated by the arrow 33, the record sheet is maintained in ataut condition. I have found it convenient to make the scale of therecord sheet, or chart, so that onetenth of an inch of movement of thechart indicates one foot of movement of the specimen III. The roller 33is, therefore, connected to a driving shaft 36 through suitablereduction gearing.

The shaft 36 is driven in timed relation to the vmovement of thespecimen I6 by connecting the electric machine 31, which is providedwith a two pole concentrated winding, the winding being connectedthrough suitable brushes to conductors 39. The dynamo-electric machine31 also has a three phase distributed winding which is connected to athree phase alternating current source of supply 4I.

The conductors 39 are connected to the winding of 'a rotatable member ofa dynamo-electric machine or self synchronous motor 42, which is likethe dynamo-electric machine 31. This rotatable member has a two poleconcentrated winding connected with the conductors 39 by suitablebrushes. The stationary member of the dynamo-electric machine 42 has athree phase distributed type winding connected by the conductors 43 tothe three phase alternating current source of supply 4I. By thisarrangement of the dynamo-electric machines 31 and 42, movement of thespecimen I0 is transmitted through the roller I2 flexible shaft 33 andmachines 31 and 42 to the shaft 33, and the chart to the resistor 44.

and the secondary coil, I prefer to introduce a balancing wave in thesecondary circuit associated with the coil I6. This balancing wave, oropposing electrical characteristic, is in the present arrangementfifty-cycle pure sine wave. so as to be the same as the alternatingcurrent source of supply I8 exciting the coils I4 and I5. The balancingwave should balance out the component of the frequency of thefundamental or harmonic, which it is desired to' study as affected bythe specimen III. This balancing wave may be equal and opposed to anelectrical characteristic of the secondary circuit of the coil I, suchas the voltage, or it may be made slightly less for convenience inobtaining a reference for measurement and comparison.

This balancing wave is introduced into the circuit by providing anon-inductive resistor 44 in series with the secondary circuit connectedacross the, coil I6. The lower terminal of the non-inductiveresistor 44is connected through suitable brushes and conductor`45 to the ad-:lustable secondary concentrated two pole winding 46 of a phase shiftingtransformer 41. The other terminal of the winding 46 is connected by aconductor 48, a lter 49, a variable resistor 50, a slider 5I, andconductor 52, to the upper end of the non-inductive resistor 44. Thefilter 49 prevents the passage of all electrical characteristics abovefifty-cycles from the winding 46 The lters 49 and I9 should be changedin accordance with the component of frequency required in the particulartest. A switch 5Ia is provided to connect and disconnect the winding 46from the resistor 44, as desired. The phase shifting transformer 41 isprovided with a three phase distributed winding, which is connected at53 toa three phase alternating current source of supply, the frequencyof the source of supply of 53 being fifty cycles to correspond with thefrequency of the alternating current source of supply I8, or otherfrequency relating the particular characteristic of the specimen I0being investigated. Any suitable manual arrangement is provided foradjusting in a zero position, but may move in either direction toindicate the voltages kin opposite directions. The field core 54 of thedynamometer is provided with a field exciting winding 58. This eldexciting winding 58 is connected across a concentrated two pole winding58 o1' a phase shifting transformer 88 through suitable .brushesv toprovide for rotation of the rotatable member carrying the winding 59. Afilter 6I is -arranged in the circuit to filter out all frequenciesabove fifty cycles, so that the field exciting winding 58 of thedynamometer is excited by a single phase fifty cycle pure sine wavealternating source of supply. The stationary member of thedynamoelectric machine 60 is provided with a three phase distributedwinding connected to an alternating current source of supply 62, whichis in the present arrangement fifty cycles but should correspond to thefrequency of the balancing wave. The rotatable member of thedynamoelectric machine 60 is also provided with a dial indicating4,three hundred and sixty electrical de- -/grees for one completerevolution. By rotation the position of the concentrated winding 46 onthe rotatable member of the phase shifting transformer 41, a scale beingprovided to indicate three hundred and sixtyelectrical degreescorresponding' to one complete revolution of the rotatable member 46.This arrangement provides for interposing into the secondary circuitassociated with the coil I6 a single phase pure sine wave alternatingcurrent of fty cycle fre,- quency, the phase relation of which can bevaried as desired by the rotation of a rotatable member 46, and themagnitude of which can be varied by an adjustment of the slider 5I onthe variable resistor 50.

Delicate measurements of the relations of the voltage, or otherelectrical characteristic, in the secondary circuit associated with thecoil I6, may be made by a dynamometer D having a field core 54 and a twopole concentrated Winding or armature 55 mounted on a suitable core androtatably supported adjacent the end of the eld core 54. The armaturecore and winding 55 are connected at 56 to an indicating hand 51, whichin the deenergized condition of the dynamometer remains of the rotatablemember carrying the winding 59 the phase relation of the voltage and thecurrent supplied to the field exciting winding 58 of the dynamometer Dcan be varied as desired. The

movable coil or armature of the dynamometer is connected to the poles 63of a two pole two position switch,shown in its open position. When thepoles 63 of the switch are closed in their upper position the armature55 is connected across the conductors I1 and I8, so as to be connectedacross the secondary circuit associated with the coil I 6. In theirlower closed position the poles 63 of the switch connect the armature 55of the dynamometer, through conduCtors 64,

across a non-inductive resistor 65, which is conof supply I8. I do thisby closing the poles 63 I of the switch to their lower position toconnect the armature B5 oi the dynamometer D across the resistor 65. Theposition of the rotatable member 59 of the phase shifting transformer 60is then adjusted until the dynamometer indicator 51,reads zero, and theangular position of the rotatable member 51 is noted. This indicatesthat the single phase in the eld exciting winding 58 of the dynamometeris in quadrature phase relation to the alternating current sourceofsupply I8. I then close the poles 63 of the two position switch intheir upper position to connect the armature 55 of the dynamometer Dacross the secondary circuit I1 and I8. The rotatable member 58 of thephase shifting transformer 60 is then adjusted until the dynamometerreads zero. This indicates that the iii'ty cycle voltage supplied fromthe rotatably adjustable winding 59 is in quadrature phase relation tothe voltage of the secondary circuit connected to the secondary coil I6.Thev phase shifting transformer 41 is now put in circuit by closing theswitch 5Ia and the rotatable member 46 is also adjusted until thedynamometer D reads zero, which indicates that the single phase fiftycycle voltage supplied from the winding 48 is also ln quadrature withthe voltage in -the secondary circuit I1 and Il. The voltage of thebalancing wave introduced atA 44 now may be ln` phase with-thevoltageand current in the secondary circuit I1 and I8, or one hundred and theadjustable winding' 46 one hundred and eighty electrical degrees andthen adjust dynamometer D to zero. In measuring the characteristics ofsome materials having very widely varying characteristics it may bedesirable not to balance -the voltage in the secondary circuit I1 "andI8 to zero with the balancing waveA interposed at 44, Abut provide for aslight unbalance by making the balancing wave slightly less than thevoltage in the secondary circuit.

After the balancing wave is introduced through accesso horizontally, lothat every magnitude variation of the curve is coordinated in relatlontothe the resistor 44 into the secondary circuit associated with the coilI6, as above described, the

specimen I0 is moved through the coils I4, I8, and I6. The variations inthe properties of the specimen I0 will affect the amplitude and phase inthe secondary circuit in accordance with the characteristics of thematerial, and the magnitude of the relative changes will be indicated bythe stylus or pen which is controlled by the solenoid 23, receivingenergy from the secondary circuit through the filter I9. The chart orrecord sheet 3| will be moved by the dynamo-electric machines 31 and 42,in accordance with the movement of the specimen I0, as indicated by thearrow 35 in Fig. l. This will cause the stylus 25 to trace a curve 68 onthe record sheet. Unless the phase relationv of the voltage and currentin the alternating current circuitaffected by the specimen I0 isdetermined, it is impossible to correctly interpret the significance ofthe magnitude changes indicated at 6B on the record sheet, which aremagnitudes functionally related to the voltage or electricalcharacteristic of the alternating current circuit affected by thespecimen. I, therefore, provide an arrangement for independently andsimultaneously indicating or recording a magnitude functionally relatedto the phase relation between the. alternating voltage and thealternating current in the alternating current circuit associated withthe coil I6, which are affected in magnitude and phase by the specimenI0 excited from the alternating current source of supply I8. Thebalancing wave thus provides an increment of an electricalcharacteristic or voltage in the secondary circuit indicative of thecondition or property of the material being tested. I preferably providean automatic arrangement for indicating or recording a magnitudefunctionally related to an electrical characteristic or voltage derivedfrom the secondary circuit affected by the material being tested, andalso for indicating or recording a magnitude functionally related to thephase angle between this electrical characteristic or voltage in thesecondary circuit affected by the material being tested and a suitablereference such as the current in the primary coil exciting circuit ofthe testing system.

This indication of phase angle is preferably recorded separately fromthe indication of magnitude shown by the curve 68, but is recorded intimed relation to the indication of magnitude 'cated by the curve 41.

magnitude -related to the phase relations indi- Such a record sheet isshownin Fig. 5.- The curve 81 is traced on the record sheet 8| by astylus or pen 88, as clearly shown in Fig. 6. The stylus 88 is mountedon its endless band 88,'which is supported in front of the recordsheet8| in the form of an elongatedloop by a plurality of rollers. Two ofthese rollers 10 and 1I vrotate about vertical axes and are mounted: onsbody member or plate 12 rigidly supportedon the body of the recorder.The spacing of thefaxesof the rollers 10 and 1I is such as to' providefor an indication of a phase angle variation of kthree hundred and sixtyelectrical /degreesjupon movement of the pen 68 from one extreme'ofitsrange of movement to the other extreme 'of' its range of movement. Theendless band lisalso supported on another larger pulley or roller 13,which is mounted so as to rotateV about avertical axis by being rigidlyattached to a vertical shaft 14. -Theshaft 14 connectstogetherthefrotatable members of the two vertically arrangeddynamo-electric ma.

chines or self synchronous motors 15 and 16. The endless band 68 isretained under tension by an idler pulleyarrangement including a pulley11 pivotally secured at 18 to a movable arm 18. The arm 'I9 is pivotedat 88 to the supporting member 12', andan arm 8i beneath the supportingmember 121s rigidly connected to the arm 18. Thearm A8Iis acted upon bya tensionspring 82 attached at 83`to the supporting member 12. The idlerpulley 11 is thus acted upon by the spring 82 withsumcient force tomaintain the desired tension in the band 68. The necessary movement ofthe roller 11 is obtained by extending the pivotal support 18 through anelongated arcuate slot .84lin the plate 12.l The particular manner ofmounting the rollers or pulleys 1I), 1I, and 11 on their supports toprovide for free rotation is shown in Fig. 10. A spindle 85 is threadedin'tothe body of the supporting member 12. The spindle 85 is providedwith a shoulder 86 secured in engagement with the supporting member12and the lower end of the roller 10 is received to receive theshoulder, and provide clearance between the bottom of the roller 10 andthe supporting member 12. The roller 10 is removably secured to thespindle 85 by a round plate 81 secured to the top of the spindle 8l by amachine screw 88. The rollers 10 and 1I are secured to the supportingmember 12 in the same manner, and the idler pulley or roller 11 issecured to the outer end of the arm 18 in a similar manner.-

The endless 4band is preferably made of thin ribbon of steeljoinedtogether at the opposite ends, as shown in Fig. 8. The ends of theribbon are cut ofi' at an angle at 68a and rounded at 88h. One end isprovided with a bayonet slot having a restricted portion 69o and anenlarged portion 68d. The ends are overlapped to cover the bayonet slot,and the other end has a pin 89e rigidly attached thereto. The pin 69eclosely fits the restricted portion 69c of the bayonet slot, and isprovided with an enlarged head tightly fitting against the side of theribbon about the slot.

The styluses 68, 88a, 68h, and 68e are al1 of to the supporting member12.

ever, to utilize a pen type stylus having an ink well provided with afine point extending in engagement with the record sheet. Thisconstruction is shown in Fig. 9. The pen 68 includes a cylindrical bodyextending vertically the width of the endless band 69. The body isprovided with an ink well 68a open at the top for convenience infilling, and a sharp pointed stylus 68h having a passage 68e thereinextending-from the ink well 68a to the sharp point 68d of the stylus.The bady of the ink well is attached to a flange 68e extending the widthof the band ,69, and is secured thereto by rivets 68j, it beingunderstood that the flange portion 68e of the stylus may be secured tothe band 69 in any other suitable manner.

The endless band 69 is retained in driving engagement with the pulley 13mounted on the shaft of the dynamo-electric machine 16, by thespringpressed idler pulley 11. The portion of the band 69 betweenrollers under tension. If vibration the band the recorder is subjectedto 69 may vibrate and cause irregular marking onthe record sheet 3|, andalso spilling ink from the well 68a. I suppress these undesirablevibrations by providing supports 12a and 12b arranged between therollers 18 and 1|, and and 13 respectively. These supports have arounded face engaging the band and extending the entire width thereof,and are secured at their lower ends by screws 12c and 12d respectivelyThe supporting member 12 is secured to the upper end-shield of the lowerdynamo-electric machine 16 by suiti able screws, and the dynamo-electricmachines or self synchronous motors 15 and 16 are secured to the body ofthe recorder by bolts extending through the feet. The shafts of thesedynamoelectric machines are arranged in vertical alignment, andconnected together at 16a by a coupling provided with set screws, whichrigidly attach the shafts of the machines together. The dynamo-electricmachines or self synchronous motors 15 and 16 are normally maintainedenergized and produce torque in opposite directions, the torque of onemachine being balanced to produce equilibrium with respect to the otherone. an arrangement is provided for actuating one or theother of themachines, so that the 'angular movement of the machine corresponds tovariations in phase relation. thus providing an angular measurement ofthe changes in phase. The dynamo-electric machines 15 and 16 constitutepolyphase electrical elements in equilibrium.

In the particular construction illustrated, one complete rotation of themachines 15 and 16, in response to phase recorded variations, is equalto three hundred and sixty electrical degrees. The pulley 13, therefore,is made of such circumference that one rotation thereof by thedynamoelectric machines 15 and 16, in recording variations in phase,equals three hundred and sixty electrical degrees. This causes the pen68 to traverse the entire distance between the rollers 18 and 1|, thedirection of movement of the pen 68 depending upon phase. The pen 68 isshown in zero degree phase position in Fig. 6 of the drawings. If theshift in phase is more than ninety degrees to the right as shown in Fig.6, the pen 68 will pass over the roller 1| passing through the positionshown in Fig. 7 of the drawings. When the pen 68 moves into thisposition shown in Fig. 7, the pen 68m moves into the position shown, sothat for a phase shift in this direction of ninety degrees the pen 68'will record the variation. On the other hand if the pen 68 undergoes aphase variation indication greater than ninety degrees, it will movearound the pulley 1| out of recording relation to the 18 and 1| alsowill be retained A record sheet 3|. However during this movement, thepen 68a will continue to indicate the recorded range of phase variationat the other side of the chart or record sheet. If thechange in phaseoccurs in the other direction, then the pen 68a will move out ofengagement with the record sheet 3|, and the pen 68 will move intoengagement therewith. The pens 68, 68a, 68h, and 68e, are all equallyspaced apart, so that whatever range of movement may occur in therotation of the pulley13, at least one of the pens 68, 68a, 68h, or 68e,will be in recording relation to the record sheet 3|. It will thus beseen that one of these pens records one range of recorded variation,whereas the other pen records another range of recorded variation. Sincethe record sheet 3| is driven in accordance with the range of movementof the material, or specimen I0, the record of variations in phaseindicated by the curve 61, and the recordy indicated by the curve 66 ofthe variations in amplitude will remain in timed relation to each other,and in timed relation to the movement of the material to be tested.

In order to r`ecord the changes in phase in the secondary circuitassociated with the secondary coil I 6, I provide an amplifier for phasemeasurement 88, which receives energy through conductors 89 and thefifty cycle band pass filter I9 from the secondary circuit associatedwith the secondary coil |6. The energy received by the amplifier 88 iswidely variable due to the changes Y caused by the speimen I8 in theelectrical characteristics of the secondary circuit associated with thesecondary coil I6. I, therefore, construct the amplifier 88 so that ithas no variable phase distortion. Whatever phase changes occur inpassing through the amplifier 88, the changes are constant withoutregard to the widely variable input from the band pass lter I9. Thedynamoelectric machines 15 and 16 are thus actuated to give a trueindication of phase, without effects of variable distortion. Thestationary member of the dynamo-electric machine 15 is provided with athree phase distributed winding connected to a suitable alternatingcurrent-'source of supply by the terminals 92, and the dynamo-elec- Itric machine 16 is also provided with a three the direction of the shiftof i terminals 93.

phase distributed winding connected to a suitable alternating currentsource of supply through the The rotatable members of'thedynamo-electric machines 15 and in suitable bearings, and each isprovided with a concentrated two pole winding connected through suitablebrushes to the conductors and 9| respectively.

The torques produced by the rotatable members of the dynamo-electricmachines 15 and 16 are opposed and equal, and as they are connected bythe coupling 16a they are in equilibrium. The torque produced by each ofthese dynamoelectric machines is in two components. One component is dueto the ux induced in the core of the rotatable member by the three phaserotating eld. In some machines this component may be small, in others itmay be large, due to the particular design. The other component of thetorque is produced by the single phase current induced to ow in theconcentrated two pole 16 are mounted -pole winding to the amplifier.

winding |20 or |22 of the rotatable members when these windings supplycurrent to an external load. If the stationary members are excited froma lthree phase source of supply and the windings |20 or |22 of therotatable members are connected to a load the rotatable members tend tooperate as inv a motor. The inputv to the winding of the rotatablemember of the dynamoelectric machine 15through the conductors 90 causesthe same to assume a position due to the concentrated two pole winding,which'is a direct measurement of the phase relation of the voltage andcurrent supplied to the rotatable member through the conductors 90. Thisis caused by the rotating field of the stationary member acting upon theflux produced by the single phase excitation of the winding .of therotatable member to a position of zero current in the winding. For thisreason, three hundred and sixty degrees of rotation of thedynamo-electric machine 15 under the action of the winding of therotatable member is equal to three hundred and sixty electrical degrees.If the concentrated two pole windings of the rotatable members of thedynamo-electric machines 15 and 16 are made four pole, or any evenmultiple of two pole. the degree of rotation of the shafts 14 indicatingthree hundred and sixty electrical degrees will be something less thanthree hundred and sixty mechanical degrees, which is well understood inthe art. If a greater number of poles were used the pulley 13 would becorrespondingly changed in size. so that the pens 68, shown in Fig. 6and in Fig. '7, would be actuated to move three hundred and sixtyelectrical degrees in accordance with three hundred and sixty electricaldegrees of movement of the rotatable members of the dynamo-electricmachines 15 and 16.

Under low, or zero, input the two pole conceny trated winding of therotatable member of the dynamo-electric machine 15 will be loaded by theamplifier 88, so that energy iiows from the two This tends to causerotation of this dynamo-electric machine. Under this condition'themachines are exactly balanced in equilibrium by supplying energy fromthe two pole concentrated winding of the rotatable member of thedynamo-electric machine 16 through the conductors 9 I. This particularmode of operation andconstruction will be more fully understood byreference to the diagrammatic illustration of Fig. 2 to be hereinaftermore fully described.

As pointed out in discussing the construction of Fig. 1, the energyreceived by the amplifier 55 for phase measurement 88 through conductors89 and the fifty cycle band pass filter I9 from the secondary circuitassociated with the coil I6 is of a very low magnitude, and widelyvariable, due to the variations produced by the characteristics of thespecimen I in passing through the coils I4, I5, and I6. The amplifier 88has such characteristics that the widely variable low power inputthereto is highly amplified to give suicient power to actuate thedynamo-electric machines 15 and 16, as required to record the variationsin phase. This amplification is affected without any variable phasedistortion between the voltage and the current from the input to theoutput of the amplifier 88. The output from the amplifier 88 is constantand whatever phase changes may occur within the amplifier 88 areconstant throughout the range of low variable energy input thereto, sothat the phase recorded by the curve 61 on the chart 3| is not affectedby icaliy in Fig. 2. The tubes employed in the circuit arrangements maybe of any suitable electron discharge type. The cathodes may be eitherdirectly or indirectly heated in any suitable manner. The manner ofheating the cathodes in l0 the tubes illustrated in the drawings is notshown,

in order to simplify the illustration in the drawings. The energysupplied to the amplifier 88 passes through several stages ofamplification, the first stage being an amplifying tube 86. Thisamplifying tube 96 is resistance coupled to the succeeding amplifyingtube by an arrangement including a plate circuit load resistor 91connected to the plate 98 of the tube, a biasing resistor 89 beingprovided for the cathode |00 of the tube 20 to control the voltage ofthe cathode within the desired range of variation. A by-pass condenser99a is provided around the resistor 99 for the alternating currentcomponent of the plate circuit. The output from the tube 96 isresistancecoupled to the succeeding amplifying tube I0| throughresistors |02 and |03, a blocking condenser |04 for the direct currentplate voltage applied to the tube 96, a variable resistor |05, and aslider |06 to the grid |01 of the tube 0|.

The variable resistor |05 is provided for the purpose of controlling theamplification of the tubes |0| and the succeeding stages ofamplification. The blocking condenser |04 provides for the free flow ofthe alternating current from the plate 98 of the amplifying tube 96 tothe grid |01 of amplifying tube |0|. The cathode |09 of the amplifyingtube I0| is provided with a biasing resistor |08 to control'the voltageof the cathode. This resistor |08 is by-passed by a condenser I I0,

so that the resistor will not interfere with the flow of alternatingcurrent in the plate circuit of amplifying tube |0I. The amplifiedoutput of the tube I0| is supplied through a push-pull type amplifyingarrangement including an iron )core 5 transformer having its primary|I|a con' nected to the plate ||2 of the tube |0I. The secondary IIIb ofthis transformer I|| is connected to grids |I2 of amplifying tubes |I3,and the mid point of the secondary I Ib is connected to -C battery. Thecathodes of the tubes ||3 are connected together at IIB and grounded at|I6. The plates ||1 of the tubes ||3 are connected across the primary|I8 of an iron core transformer I I9l and the mid point of the primaryII8 is connected to +B battery. The secondary ,of the transformer ||9 isconnected across a two pole concentrated winding |20 of thedynamoelectric machine 15 through conductors 90 and suitable brushes ofthe machine. The secondary of the transformer I|9 is tapped to lprovidefor matching the impedance of the plate circuit of the tubes IIS By thisarrangement, the amplified output from the tube I0| throughl thetransformer III, tubes |I3, and transformer ||9 is supplied to the twopole concentrated winding |20 of the dynamo-electric machine 15.

The stationary member of the dynamo-electric machine or self synchronousmotor 15 is provided with a three phase distributed winding connected toa fifty cycle alternating current source of supply I2I, which is alsoconnected to the three phase distributed winding of the sta-- tionarymember of the dynamo-electric machine or self synchronous motor 16. Theoutput from the transformer Iv|9 excites the two pole concen- `input, soas to divert trated winding |28 of the rotatable member of thedynamo-electric machine ,15, and causes the rotatable member to moveinto a position angu` In order to obtain substantially constant power,

output for actuating the dynamo-electric machine in recording phase, Iprovide an arrangement in the amplifying electron discharge circuitsbetween the input 81 and the output 98 of the amplifier 88, theamplifying circuit in direct proportion to the increase in energy, andconversely decreases the diversion o! energy in the same proportion asthe input decreases. This is done by providwhich diverts energyfromprevent the flow of B battery current through the succeeding tubes,but providing for the flow of the desired alternating current. Thecathode of the tube |3| is provided with a biasing resistor |38, whichis provided with a by-pass condenser |31 connected across the same, soas not to interfere with the flow of alternating current in the platecircuit of the tube. The output from the amplifying tube |3| is to theplate |39 of a rectifying tube |38 having a plate loading resistor |48,which is grounded. 'I'he cathode |4| of the rectifying tube |38 isgrounded through a biasing resistor |42, and a by-pass condenser |43 foralternating current or undesirable pulsations. The upper end of-thebiasing resistor |42 is positive and connected to the grids |26a of thetubes |23 through a resistor |44.

- This resistor or choke |44 must be made sutiling an electron dischargecircuit including two tubes 23 having their plates |24 connected at theopposite sides of the resistor |03, and their cathodes |25 grounded at|26 through a battery |21, the positive side thereof being connected tothe cathodes. The number of tubes |23 may be varied as required toobtain the required load capacity and range of voltage variation. Underthe conditions of low energy input the grids l28a of the tubes thebattery |21, as the grids |260. are then at ground potential, so that noenergy is diverted from the amplifying circuit through the tubes |23.Upon increase of input to the amplifier the grids |28a of the tubes |23have their bias voltage raised in direct proportion to the increasedserve as variable resistors to the ow of energy through the tubes by wayof their platecircuits. l

The constant output at 98 from` the amplier 88 is indicated by the curve98a in Fig. 3, and the energy diverted through the tubes |23 1nproportion to theA increased input to maintain constant output isindicated by the dotted curve |23a l in Fig. 3. l

The necessary control of the grids |28a to obtain this result isobtained by making a connection at ing tube 9S and the resistor |82,which is connected to ground through a blocking condenser |28a forblocking the plate voltage on the plate 98, and permitting the desiredalternating current to pass therethrough, and through a resistor 28having a slide 23 connected to the grid |38 o f an amplifying tube |3I.By making the connection at |21a the tendency for the increased input tooverloady the amplifying tube |3| is avoided, because the increasedinput is immediately diverted through the tubes |23. The slider |29controls the amplification in the tube |3|. The plate |32 of the tube|3| has a plate circuit load resistor |33 connected between the plate|32 and the +B battery. The output from the tube |3| is through ablocking condenser |34, to

energy from the amplifying tubes |23 by way of the |21a between theplate 98 of the amplify- 23 are biased beyond cut-oi by ciently large toprevent any feedback through the tubes |23 to the input of theamplifying tube |8I, and also to suppress any undesirable ripples in thevoltage on the grids |26a. Alternating current or pulsations are furthercarried from the grids |26a to ground through by-pass condenser |44a.Such ripples or pulsations would be reected into the amplifying circuitsand interfere withv the smooth operation of the ampli- 11er in theoperation of the phase recorder. By this arrangement the energy derivedfrom the output of the amplifying tube 96, through the amplifying tube|3I, and the rectifying tube |38 controls the voltage on the grids |26aof the tubes |23, so as to divert energy from the amplitying circuit, asindicated by the dotted line |23a in Fig. 3,- thus maintaining constantoutput from the amplifier 88;

In the amplifier 88 shown in Fig. 2, the resistors and the tubes may beselected to meet any.

particular requirements of design. However, if the values are chosen sothat the resistors |82 and |83 each have one unit of resistance, theresistor |86 has five units of resistance, and the tubes |23 are biasedbeyond cut-off to provide ini'lnite resistance, the output of the tube96 is divided across seven units of resistance, the impedance of thecondenser |84 being negligible as compared to the values of theresistors, then the input to tube |8| would be 5/7 of the output of tube83.

At the maximum grid bias the direct current plate resistance of each ofthe tubes 23 was chosen, so that the alternating current output from theplate of the tube 96 was divided across the resistor |82 and theplate-resistance of the tube |23 to give approximately 1/5 of the outputof the tube 96 at the point |21a. The alternating current voltage at theplate of the second tube |23, or the input to the tube |8| wasapproximately 3&5 of the output of the tube 96. If a third tube |23 wereadded then the input to the tube |8| would be approximately 1/125 of theoutput of the tube 96. If a fourth tube were added then the input to thetube |8| would be approximately 1/ of the output of the tube 96.

It will thus be seen that: two tubes |23 aiord a voltage ratio of at to1,55 or about 18 to 1; three tubes |23 aii'ord a voltage ratio of 5/1 to1/125 or about 89 to 1; and four tubes afford a voltage ratio of @t to14,25 or about 446 to 1.' The number of tubes may be varied to obtainany desired variation.

I have obtained an even greater range of voltage variation by doublingthe values of the resistors |82, |83, and I 85. Under this conditionwhen the tubes |23 are biased beyond cut-oil? to provide infiniteresistance, the output of the tube 88 was divided across theeresistorsso that the input to the tube was V; ofthe output of the tube 88. Atmaximum bias of the tubes |28 the alternating current voltage wasdivided so that: the voltage at the plate of the first tube |28 wasabout 1,6 of the output of the tube 88; the voltage at the plate of thesecond tube |28 or the input to the tube |0| was 1,61 of the, output ofthe tube 08; the voltage at the plate of -a third tube |28, if added.would be about 1,1129 ofthe output of tube 88; and the voltage at theplate of` a fourth tube |23, if added, would be $6531 of the output ofthe tube 88. With this doubling of resistors |02, |08, and the range ofvoltage variation afforded by the tubes |28 is as follows: two tubesabout 58 tc 1; three tubes about 520 to l; yand four tubes about 4685 to1.

When the input to the amplifier 88 decreases to a small value, somewherebetween O and X, as indicated in Fig. 3, the tubes ||8 provide a loadtubes |28. Tho alternating current is impressed on the grid |51 of. theamplifying tube |88 through a slider |58 of a variable resistor |80con-v nected between the condenser |58 and ground. The slider |58provides for control of the amplification of the tube |58. The tube |58is provided with a cathode |8|', a biasing resistor |82, and aV Theoutput ofthe amplifying tube |58 is through aplate circuit loadingresistor |84 connectedto the plate |85 orf the tube. The plate |85 ofthe tube |58 is connected to an output circuit through a blockingcondenser |88 for the direct,current for the two pole concentratedwindingy |20 of the rotatable member of the dynamo-electric 'machine 15.As the stationary winding of the dynamo-electric machine is of the threephase distributed type, this loading o the two pole concentrated windingtends to cause the same to operate as a motor. In order to oppose therotatable member of the dynamo-electric machine 15, to maintain the samein equilibrium under these conditions, the two pole concentrated winding|22 of the rotatable member of the dynamo-electric machine 18 is loadedby an amplifying and rectifying tube arrangement now to be described, soas to balance the torque exerted by the dynamo-electric machine 15. Thetwo pole concentrated winding |22 of the dynamoelectric machine 18 isconnected by conductors 9| and a variable resistor Sla across thesecond- Vary of the iron core transformer |45. The primary of thistransformer is connected to plates |48 or amplifying tubes |41, thecathodes |48 of these tubes being connected together at |48 and groundedat |50. The mid point of the primary of transformer |45 is conected to+B battery. The grids itill of the tubes |41 are connected together at|52, a 'oy-pass condenser |58 being provided to by-pass to ground anyundesirable pulsations or alternating current. Under this condition ofzero or low input the tubes |41 load the 5,

two pole concentrated winding |22 of the dynamo-electric machine 18, sothat the dynamoelectric machines 15 and 18 are opposed in torque and inequilibrium. The grids |5| of the tubes plate voltage, but which passesthe desired alternating current to the cathode |81 of a rectifying tube|88. The cathode |81 has a biasing resistor |68 connected between thecathode and ground. The plate |10 of the tube |88 is connected to anoutput circuit including a loading resistor |1| and a by-pass condenser|12 for bypassing any. undesirable pulsations or alternating current.The output of the plate circuit of the rectifying ,tube |88 is connectedto the grids |'5| of the tubes |41 through a resistor |18. `By thisarrangement, as soon as the input to the amplirler 88 increases theenergy is supplied through the conductor |55 to the amplifying tube |58the rectifying tube |88, so as to immediately supply a voltage throughthe resistor |12 to the grids |5| and bias the tubes. |41 beyondcut-off, thus immediately preventing any further loading of the two poleconcentrated winding |22 of the dynamo-electric machine 18 by the tubes|41. Under this condition the dynamo-electric machine 15 will beactuated to assume an angular position depending upon the phase relationof the voltage and the current supplied from the transformer |41 are atzero bias, so that they do not inter- 5 fere with the ow of currentthrough the tubes. As soon as the power input to the ampliiier 88increases itis apparent that there will be a reversed fiow of current inthe output leads 80, so that energy will be supplied from the tubes ||8through the transformer ||8 to the two pole concentrated winding |20 ofthe dynamo-electric machine 15. The grids |5| ofthe tubes |41 then mustbe immediately biased beyond cut-oil'. so as to cut off the flow ofcurrent in the plate circuit' through the primary of the transformer|45. When this occurs the winding |22 of the dynamo-electric machine 18is no longer loaded through the tubes |41.

This rapid response` is obtained by making a connection at |54 in theplate circuit of the tube |23 and between the resistors |02 and |03.Thus the increased input causes a ilow of energy through the conductor|55, and the blocking condenser |58 for the direct plate current ofy the||9 through the conductors 80 to the two-pole concentrated winding |20.

The characteristics of operation oef this ampliiler will be clear from aconsideration of the curve shown in Fig. 3. At zero load theplatecurrent of the tubes |41 is indicated by OW.

' During the incremental increase of initial input O to X, the platecurrent of the tubes |41 is reduced to zero, as indicated by the dottedcurve |41a. During this interval the output of the amplier is increasedgradually as indicated by the line OY, and then becomes constantthroughout the further range of increase as indicated at 88a by the lineYZ. At the point X, it will be noted that the curve |23a is zero, but itincreases in direct proportion to the input, which indicates that theenergy diverted from the amplifier 88- through the tubes |28 keeps theoutput' constant. It is to be understood, of course, that these curvesrepresent the relation without taking into effect distortion, but thismay be minimized by proper design.

The operation of the foregoing construction and the particular methodemployed in the operation of the system will be clear from the foregoingdescription, however, the entire operation now will be brieflydescribed. The specimen I0 may be any suitable length of material thecharacteristics of which are to be determined. These characteristics maybe determined by carrying out and recording the test of the specimen andthen comparing the curves obtained in the recorder 24 with the knownstandard properties. or another specimen the properties of which havebeen previously determined by testing in the system. Preparatory tomaking the test, the specimen |0 is extended through the primaryexciting coils i4 and i5 and the secondary coil I8, and a by-passcondenser |88 connected thereto.

` incremental input to with variations in balancing wave 4of suitablemagnitude is introduced into the secondary circuits |'I and I8 acrossthe nan-inductive resistor 4L In making the tes. the Specimen I issupported on the rollers and |2 in coaxial relation with the excitingcoils I4, l5, and the secondary coil I8, and the specimen is movedthrough the coils either manually, or by the driving arrangementindicated at I3, at a uniform speed suitable for the making of the test.The variations in the properties or characteristics of the specimen |'6affect thesecondary coil I6 and the secondary circuits l1 and |3associated therewith, and these effects are utilized to determine thecharacteristics of the specimen I0. A magnitude functionally related toan electrical characteristic of the secondary circuits I1 and |8affected by the characteristics of the specimen I0 is recorded bysupplying energy from the fty cycle .band pass filter I9 throughconductors 20 to a voltage amplifier 2|, and energy is supplied from thevoltage amplifier 2| through conductors 22 to asta,-

tionary solenoid 23 of the recorder 2l. Thus thearmature 30 is actedupon by the solenoid 23, so as to actuate the arm 26 and cause thestylus 25 to make a record of amplitude on the record sheet 3| incoordinated or timed relation with the movement of the specimen, whichoperates the record sheet 3| through the roller |2 in contact with thespecimen, flexible shaft 38, dynamo-electric machines 31 and 42 and theshaft 36. By this arrangement, the amplitude variation shown by thecurve 63 is a record of a magnitude functionally related to theelectrical characteristics of the secondary circuit and I8 associatedwith the secondary coil I6, which is affected by the characteristics ofthe specimen I0 excited by the primary coils Il and i5 from thealternating current source of supply |3- As previously explained, unlessthe curve of magnitude 66 indicated on the record sheet 3| is relatedalso to the phase relation of the voltage and thecurrent in thesecondary circuit and I8 associated with the secondary coil I6, theobserved results' may be very misleading, because phase relation andmagnitude must be coordinately taken into consideration to determine theproperties of the specimen I0. Variations inphase are shown by thecurve.6|, which is traced on the moving chart 3| by pen or stylus 68, asclearly shown in Figs. 1, 4, and 6. The styluses 38, 68a, 6817, and 88ecarried by the endless band 69 are controlled, so as to obtain thedesired indication of variations in phase by the dynamo-electricmachines or self synchronous motors '15 and '16', which are in opposedtorque relation and in equilibrium throughout their range orf movement.Under low input to the amplifier 88 the dynamo-electric machine isloaded by the ampliier 38 through the conductors 90, so that it tends tooperate as a motor. This is opposed and balanced to a condition ofequilibrium by the action olf the dynamo-electric machine 76, which issimilarly loaded through the conductors 9| from the ampliiier 88, asexplained in connection with the description of the construction andoperation of the amplifier 88 shown in Fig. 2. Beyond a low the amplier88 the dynamo-electric machine 76 is no longer loaded by the ampliiier88 through the conductors 9 Under this condition-the dynamo-electricmachines l5 and 16 are librium, and actuated to producing opposed torquein equithe dynamo-electric machine 'l5 is from the spirit and phase.This causes the pulley 13 to operate the band 69 and one or more of the.styluses 88, 68a, 68h, or 68o trace the curve of phase variation asindicated at 61 in Figs. 1 and 5.

It win thus be seen that 1 have provided an improved system andy methodfor testing ma.- terials in which the material is utilized to aiiect an.electrical characteristic of an alternating current circuit, andthesalternating current circuit variations produced by the'characteristics of the specimen are recorded, as to magnitude andphase, in coordinated relation to each other and to themovement of thespecimen l0.

I do not desire my invention to be limited to the particularconstruction and method described, and I intend in the appended claimsto cover all modifications, winch do not depart scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. A method of testing the properties of a material in which thematerial affects a phase relation and an electrical characteristic of analternating current circuit including: indicating a magnitudefunctionally related to the phase angle between an alternating currentand an alternating voltage in the circuit, and indicating a magnitudefunctionally related to an alternating electrical characteristic of thecircuit simultaneously with and independently of indicating themagnitude related to the phase angle.

its angular position in accordance 2. A method oi' testing theproperties of a material in which the material affects a phase relationand an electrical characteristic of an alternating current circuitincluding: recording a magnitude functionally related to the phase angiebetween an alternating current andan alternating voltage in the circuit,and recording a magnitude functionally related to an electricalcharacteristic of the circuit simultaneously with and independently ofthe recording of the magnitude related to the phase angle with theamplitudes of the magnitudes arranged in timed relation.

3. A method of testing the properties of a material in which thematerial affects a phase relation and an electrical characteristic of analternating current circuit and in which the material is moved withrespect lto the alternating current circuit including: indicating amagnitude functionally related to the phase angle between an alternatingcurrent in the circuit;`

and an alternating voltage in the circuit, indicating a magnitudefunctionally related to an electrical characteristic od the circuit intimed relation to the magnitude relating to the phase angle, andindicating the phase angle and electrical characteristic in timedrelation to the movement of the material.

4. A method of testing the properties of a material in which thematerial affects a phase relation and an electrical characteristic of analternating current circuit and in which the material is moved withrespect to the alternating current circuit including: indicating amagnitude functionally related to the phase angle between an alternatingcurrent and an alternating voltage in the circuit during the entirerange of movement of the material, and indicating a magnitudefunctionally characteristic ci the circuit simultaneously with theindication of the magnitude relating to the phase angle during theentire range of movement of the material. A

related to an electrical.

5. A method of testing the properties of a material in which themateria-l affects a phase relation and an electrical characteristic ofan alternating current circuit and in which the material is moved withrespect to the alternating current circuit. including: recording amagnitude functionally related to the phase angle between an alternatingcurrent and an alternating voltage in the circuit during the entirerange of movement oi the material, recording a magnitude functionallyrelated to an electrical characteristic of the circuit simultaneouslywith the recording of the magnitude related to the phase angle duringthe entire range of movement of the material, and recording themagnitudes related to the phase angle and the electrical characteristicin timed relation to each other-and in timed relation to the movement ofthe material.

6- A method of testing the properties of a material in which thematerial affects a phase relation and an electrical characteristic of analternating current circuit and in which the material is moved withrespect to the alternating current circuit including: recording amagnitude functionally related to the phase angle between an alternatingcurrent and an alternating voltage in the circuit, recording a magnitudefunctionally related to an electrical characteristic of the circuitseparately from the magnitude related to the phase of the alternatingcurrent, and timing the recording of the magnitudes relative to eachother and relative to the movement of the material.

7. A method of testing the properties of a material in vwhich thematerial is excited from an alternating current source and in which theexcited material affects a phase relation and an electricalcharacteristic of an alternating current circuit including: exciting'thematerial with an alternating current, electrically filtering all excepta selected frequency suppliedfrom-thacircuit, indicating an electricalcharacteristic supplied from the filter, and indicating the phaserelation oi' the alternating electrical characteristic and thealternating current in the alternating current circuit. Y

8. A method of testing the properties of a material in which thematerial is excited from an alternating current source and in'which theexcited material affects a phase relation and an electricalcharacteristic of an alternating current circuit including: exciting thematerial froma pure sine wave alternating source, electrically filteringall except a selected frequency supplied from the circuit, indicating anelectrical characteristic supplied from the filter, and indicating thephase annesso terial in which the material is excited from analternating current source and in which the excited material adects aphase relation and an electrical characteristic of an alternatingcurrent circuit including: exciting the material from an alternatingcurrent source of supply. interposing a balancing wave of the samefrequency as the source of supply in the circuit and in opposition tothe -voltage in the circuit to provide a reference for measurement,electrically filtering all frequencies higher than the frequency of thesource of supply, recording an electrical characteristic supplied fromthe filter, and recording the phase relation of the voltage and thecurrent in the alternating current circuit in timed relation to therecorded electrical characteristic.

11. A method of testing the properties of a material in which thematerial is excited from an alternating current source and in which theexcited material afi'ects a phase relation and an electricalcharacteristic of an alternating current circuit and in which thematerial is moved with respect .to the alternating current circuitincluding: exciting the circuit with an alternating current, interposinga balancing wave in the circuit and in opposition to an electricalcharacteristic in the circuit to provide a reference for measurement,electrically filtering all except a selectedY range of frequency fromthe circuit, recording an electrical characteristic supplied from thefilter, and recording the phase relation of the electricalcharacteristicr supplied from the filter and the Ycurreniin thealternating current circuit in timed relation to the electricalcharacteristic and in timed relation to the movement of the material.

12. An apparatus for testing the properties of a material including analternating current circuit arranged in cooperative relation with saidmaterial, means for exciting said alternating current circuit, 'meansfor indicating an alternating electrical characteristic in saidalternating currelation-ofthe electrical characteristic supplied v fromthe filter and the alternating current in the alternating currentexciting circuit.

9. A method of testing the properties of a material in which thematerial is excited from an alternating current source and in which theexcited material aifects a phase relation and an electricalcharacteristic of an alternating current circuit including: exciting thematerial with an alternating current, interposing a balancing wave inthe circuit in opposition to an electrical characteristic in the circuitto provide a reference for measurement, electrically filtering allexcept a selected frequency from the circuit, indicating an alternatingelectrical characteristic supplied from the filter, and indicating thephase relation of voltage and current in the alternating currentcircuit.

10. A method of testing the properties of a marent-circuit, and meansfor indicating the phase relation between the voltage and the current insaid alternating current circuit separate from said electricalcharacteristic indicating means and in timed relation to saidalternating electrical characteristic.

13. An apparatus for testing the properties of a material including analternating current circuit arranged in cooperative relation with saidmaterial, means for moving said material with respect to saidalternating current circuit, means for exciting said alternating currentcircuit,

means for indicating an alternating electrical characteristic in saidalternating current circuit, and means for indicating the phase relationbetween the voltage and the current in said alternating current circuitseparate from said voltage indicating means and in timed relation tosaid alternating electrical characteristic and to the movement of saidmaterial.

14. An apparatus for testing the properties of a ymaterial including analternating current circuit,

means for exciting said alternating current circuit from an alternatingcurrent source of supply, means utilizing said material for affectingthe amplitude and phase of the electrical characteristics of saidcircuit in accordance with the characteristics of said material, meansincluding an amplifier for indicating the change in amplitude of anelectrical characteristic of said alternating current circuit, and meansincluding an ampliner responsive to an electrical characteristic of saidalternating current circuit and operating without variable phasedistortion for indicating the phase relation between the voltage andcurrent in said alternating current circuit.

15. An' apparatus for testing the properties of a material including analternating current circuit, means for exciting said alternating currentcircuit from an alternating current source of supply, means utilizingsaid material for affecting the amplitude and phase of the electricalcharacteristics of said circuit in accordance with the characteristicsof said material, means including an amplifier for indicating the changein amplitude of an electrical characteristic oi' said alternatingcurrent circuit, and means including an amplifier responsive to anelectrical characteristic of said alternating current circuit andoperating without variable phase distortion for indicating the phaserelation between the voltage and current in said alternating currentcircuit in timed relation to the indication of the alternating currentcircuit through said filter change in amplitude of said electricalcharactercircuit in accordance with the characteristics of the material,means supplied from said alternating current circuit for electricallyfiltering all except a selected frequency, means for indicating theamplitude of the electrical characteristie corresponding to saidselected frequency, and means including an amplifier actuated by theoutput from said filtering means and operating without variable phasedistortion for indicating the phase relation between the selectedfrequency and the alternating current of the alternating currentcircuit.

17. An apparatus for testing the properties o f a material including analternating current circuit arranged in cooperative relation with saidmaterial, means including an amplifier for indicating the alternatingvoltage in said alternating current circuit, means including a filterfor supplying a selected frequency of the voltage to said alternatingvoltage indicator, and means receiving energy from said alternatingcurrent circuit through said lter for indicating the phase relation ofvoltage from the filter and an electrical characteristic of saidalternating current circuit.

18. An apparatus f or testing the properties of a material including analternating current circuit arranged in cooperative relation with saidmaterial, means including an amplifier for indicating an alternatingelectrical characteristic in said alternating current circuit, meansincluding a filter for supplying from said alternating current circuit aselected frequency of an electrical characteristic to said electricalcharacteristie indicator, and means receiving widely varying energy fromsaid alternating current circuit through said filter for indicating thephase relation of an electrical characteristic from said filter and anelectrical characteristic of said alternating current circuit.

19. An 'apparatus for testing the properties of a material including analternating current circuit arranged in cooperative relation with saidmaterial, means for indicating an alternating electrical characteristicin said alternating cur'- and providing substantially'constantrelatively high energy output for indicating the phase relation of anelectrical characteristic from said lter and an' electricalcharacteristic of said alternating current circuit.

20. An apparatus for testing the properties of a material including analternating current circuit arranged in 4cooperative relation withl saidmaterial, said alternating current circuit providing low energy outputwidely variable in .accordance withchanges in the characteristics ofsaid material, and means including a constant output amplifier receivingvariable input from said alternating current circuit and maintainingconstant phase over the range of low variableenergy input for recordingthe phase relation, of the voltage and the current in said alternatingcurrent circuit.

21. A method of testing the properties oi' a material in which thematerial is excited by an alternating current to .produce an alternatingflux therein, in which the vcondition or property of the material beingtested is indicated in a circuit affected by the material, and in whichthe phase angle between the alternating voltage in the circuit affectedby the material beingtested may be any phase angle with respect to thealternating current producing the alternating ux dependent upon theproperty of the material including: automatically indicating a magnitudefunctionally related to the' phase angle between the alternating currentproducing the alternating ux in the material being tested and analternating voltage in the circuit affected by the material, andautomatically indicating a magnitude functionally related to analternating voltage of the circuit affected by the materialsimultaneously with and independently of indicating the magnituderelated to the phasey angle.

22. An`apparatus for testing the properties of material in which the.phase angle between the alternating voltage in the circuit affected bythe material being tested and the alternating current producing thealternating fiux. is dependent upon the property of the material beingtested including means exciting the material for producing therein anvalternating flux, a circuit electrically affected by the material, meansfor automatically indicating a magnitude functionally related to thephase angle between the alternating current producing the alternatingflux in the material and an alternating voltage in the circuit affectedby the material, and means for automatically indicating a magnitudefunctionally related to an alternating voltage in the circuit aected bythe material simultaneously with and independently of indicating themagnitude related to the phase angle.

23. A method of testing the properties of material in which the materialis excited by an alternating current to produce therein an alternatingux, in which the condition or property of the material being tested isindicated in a circuit aiiected by the material, and in which the phaseangle between the alternating voltage in the circuit affected by thematerial being tested may be any phase angle with respect to analternating current of suitable reference depending upon the property ofthe material including:

rent circuit, means including a filter for supplyproviding an incrementoi voltagein the circuit affected by the material being tested.indicating a magnitude functionally related to the phase anglebetween'the alternating current oi `reference\and said increment ofalternating voltage in the circuit ailected by the material, andinditernating flux. a circuit electrically ailected by the material,means associated with said circuit 20 for providing an increment of anelectrical characteristic indicative of a condition or .property of thematerial being tested, means for indicating a magnitude functionallyrelated to the phase angle between said alternating current of referenceand said increment oi alternating voltage in the circuit aiiected by thematerial, and means indicating the magnitude functionally.re1ated tosaid increment of alternating voltage in said circuit atiected by saidmaterial simultaneously with and independently of indicating said mag.

nitude related to the phase angle.

25. A method of testing the properties of ma.- terial in which thematerial is excited by an alternating current to produce therein analternating ilux, and in which a plurality oi the conditions orproperties oi the material being tested arelndicated in a circuit byvarious electrical characteristic magnitudes and phase angles oi themagnitudes with respect to a suitable reierence corresponding with theparticular condition or property of the material being determined by theelectrical test including: indicating an electrical characteristic inthe circuit affected by the material being tested, and indicating amagnitude functionally related to various phase angles between thealternating current of reference and the electrical characteristic inthe circuit affected by the material corresponding to the `particularproperties of the material being determined inthe electrical test.

- EMME'II' M. IRWIN.

